1. Field of the Invention
The present invention relates to a gas turbine cooled moving blade in which a cooling air supply passage, connected to a moving blade, is improved so that temperature elevation and pressure drop of cooling air on the way to the moving blade are suppressed.
2. Description of the Prior Art
FIG. 3 is a cross sectional view showing a prior art air cooled system of a moving blade in a gas turbine inlet portion. In the figure, numeral 21 designates a first stage moving blade, numeral 22 designates a platform thereof, numeral 23 designates a blade root portion and numeral 24 designates a shank portion of a lower portion of the platform 22. Numeral 31 designates a stationary blade, which is adjacent to the moving blade 21, numeral 32 designates an inner shroud thereof, numeral 33 designates a cavity in a lower portion of the inner shroud 32 and numeral 34 designates an outer shroud. Numeral 40 designates a rotor disc, numeral 41 designates a disc cavity and numeral 42 designates a radial hole, which is bored in the rotor disc 40 for supplying cooling air therethrough.
The moving blade 21 is arranged alternately with the stationary blade 31 in a rotor axial direction and is fixed to the rotor disc 40 via plural pieces along a rotor circumferential direction, so that the rotor may be driven rotatably due to combustion gas 60 coming from a combustor.
In the gas turbine constructed as above, cooling of the moving blade is achieved by the cooling air, for which a portion of rotor cooling air is used. That is, cooling air 50 flows into the disc cavity 41 and is led into the blade root portion 23 via the radial hole 42 provided in the rotor disc 40. And then, the cooling air passes through the shank portion 24 and the platform 22, flows into an air passage (not shown) provided in a blade interior for cooling of the blade and is discharged into a combustion gas passage through a blade surface or a blade trailing edge portion.
In the prior art arrangements cooling for the gas turbine moving blade, cooling air from a rotor cooling system is led from the disc cavity 41 into the air passage for cooling the moving blade through the radial hole 42, the blade root portion 23, the shank portion 24 and the platform 22, as mentioned above. However, as the cooling air 50 is led into the moving blade 21 interior, the cooling air receives heat from the rotor disc etc. so as to become elevated in temperature, and pressure thereof is lowered, so that there occurs a loss until the cooling air is supplied into the air passage in the moving blade 21. Thus, in order to enhance cooling efficiency, it is necessary to lessen such temperature elevation and pressure loss of the cooling air to the extent possible.